The use of a stabilizing amount of thymol, among other substances, in methylene chloride has been disclosed in U.S. Pat. No. 2,008,680. This is stabilization against chemical decomposition with commensurate acid development. Similarly, U.S. Pat. No. 2,155,723 has disclosed the like serviceability of, for example, pentaphen (p-tert-amyl phenol), when used in trichlorethylene.
The presence of minor amounts of these stabilizers such as pentaphen, as for example only a few hundred parts per million up to a few hundredths weight percent, has heretofore been shown in the solvent phosphatizing art. Thus, in U.S. Pat. No. 3,361,598, 0.01 weight percent of pentaphen is used along with trichlorethylene in many of the exemplary compositions taught in the patent. With regard, however, to providing coatings, a trichlorethylene-based phosphatizing composition containing 150 parts per million pentaphen did not perform more effectively than a stabilizer-free composition. Such lack of phosphatizing effect has been discussed in U.S. Pat. No. 3,475,228.
Further, the presence of up to 0.03 percent of pentaphen or thymol has actually been found to be unsatisfactory. This is for stabilizing trichlorethylene-based phosphatizing compositions, as has been taught in U.S. Pat. No. 3,281,285. The prior art has also discussed coating performance for such stabilizer-containing compositions, wherein the stabilizer pentaphen is present at the elevated, about 0.01 percent level. U.S. Pat. No. 3,277,120 has shown that a phosphatizing composition containing such level of pentaphen does not provide for satisfactory coating performance.
In pending application Ser. No. 560,378, now U.S. Pat. No. 4,008,101, there are disclosed phosphatizing compositions which contain methylene chloride and water, while having a continuous and homogeneous liquid phase. Such compositions can provide phosphatized coatings having at least substantial water insolubility. The liquid phase contains water in minor amount, thus retaining the desirable process characteristics associated with solvent phosphatizing.
Such compositions may also contain stabilizer, and it has been taught to typically prepare same to contain about 0.03 weight percent of a stabilizer such as pentaphen. Further, the use of a stabilizer-containing adjuvant composition is disclosed. Such adjuvant might be expected to contain up to one weight percent of stabilizer.
Resulting phosphatizing metal surfaces are often topcoated. Topcoating can be done with a variety of paints or the like. It would be desirable to achieve excellent topcoat adhesion for such later applied coating compositions.